Numerous diseases (tuberculosis, pneumonia, urinary pathologies, etc.) that have been well under control since the advent of antibiotics now constitute reemerging pathologies, often with a fatal prognosis, as a consequence of the impotence of classic antibiotics.
In fact, tuberculosis, formerly an implacable scourge (caused by the bacillus Mycobacterium tuberculosis), had regressed in the last forty years in the industrialized countries due to the amelioration of social conditions and to the application of an efficacious antibiotic treatment. It reappeared in a more virulent form in the middle of the 1980's in numerous countries, including France and the United States. The “new” forms of the bacillus are resistant to classic tuberculosis drugs (streptomycin, isoniazid, rifampicin) as well as to other antibiotics, which are hardly efficacious.
Likewise, the infections called _“nosocomial_” frequently contracted in a hospital environment are most often very difficult to bring under control on account of their resistance to available antibiotics. 20 to 25% of pneumococci isolated in a hospital environment turned out to be resistant to the antibiotics of the family of macrolides and 20 to 40% of the Staphylococcus aurei isolated in hospitals in the USA are resistant to methicillin.
The existence and constant appearance of bacteria that are more and more resistant to antibiotics is putting a significant demand on the pharmaceutical industry and making it absolutely necessary to discover new families of antibiotics.
The marine biotope is considered the richest of the various habitats of the globe, but also is the least well known by scientists. It is also the prebiotic cradle of our planet (3 billion years of evolution). As a consequence, this provides a diversity of species, systems of organization, forms and adaptive solutions. This biodiversity is a source of a formidable chemodiversity, a potential source of new natural compounds. Research has already led to the discovery of substances that are remarkable on account of their structures as well as their biological activities. Several thousands of substances have been indexed. More than 150 publications describing new secondary metabolites have appeared each year for more than 10 years. Some of these metabolites constitute subject matter of clinical trials or have already been commercialized. Other compounds such as toxins from marine microorganisms (ciquatoxin, brevetoxin, saxitoxin or tetrodotoxid) are tools of choice in neurophysiology and in particular in the study of ionic channels.
At the present time, more than one half of molecules with a marine origin capable of being used in the health field are intended for the treatment of cancers. In twenty-five years, from 1970 to 1995, more than 130 marine substances were patented in the world for their therapeutic properties.
Curiously, the area of antibiotics has been somewhat forgotten. The investigation of new antibiotic peptides in marine invertebrates has only been very recently approached. Antimicrobial peptides are molecules whose target is the bacterial membrane. Consequently, to acquire a resistance to these type of molecules, the microorganisms must change the composition and organization of their membrane lipids. This solution, which is costly from an evolutionary viewpoint, explains why the resistance of microorganisms to this type of antibiotics is only rarely referenced.